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Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi; Kanno, Ikuo
Journal of Nuclear Science and Technology, 8 Pages, 2024/00
Times Cited Count：0 Percentile：0.08(Nuclear Science & Technology)Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi
Journal of Nuclear Science and Technology, 59(4), p.424 - 430, 2022/04
Times Cited Count：1 Percentile：15.7(Nuclear Science & Technology)Koura, Hiroyuki
RIKEN Accelerator Progress Report, Vol.38, P. 9, 2005/05
We calculate proton-emission partial half lives and discuss dominant decay modes in the heavy and superheavy nuclidic region. The proton-emission partial half-lives are calculated from the one-dimensional WKB method with single-proton potentials and a mass formula that our group has developed. The calculated half lives well reproduce experimental ones in order of 100 or 1/100 which is similar predictability to other predictions as the alpha decay and the beta decay. We apply this result to calculation of branching ratios of nuclear decays considered the alpha decay, beta decay and spontaneous fission in the heavy and superheavy nuclide region. In this analysis we point out that proton-emitting nuclei are expected to be in the unknown proton-rich nuclidic region with 
. On the other hand, proton-rich nuclei with 
have much shorter spontaneous-fission half-lives than ones of proton emissions on this calculation, therefore we conclude that ground-state proton emissions would not occur in that region.
CfShinohara, Nobuo; ; *; Tsukada, Kazuaki*; Otsuki, Tsutomu*; J.Alstad*
Radiochimica Acta, 56, p.127 - 131, 1992/00
no abstracts in English
Cm by absolute fission track countingUsuda, Shigekazu; Umezawa, Hirokazu
Nucl. Tracks Radiat. Meas., 16(4), p.247 - 251, 1989/00
no abstracts in English
Es targetAsai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.
no journal, ,
Spontaneous fissions of 
Fm, 
Fm, and 
Lr have been measured using an Es target at the JAEA Tandem Accelerator Facility. These three nuclei show different fission properties: the asymmetric fission, the high total-kinetic-energy (TKE) symmetric fission, and the low TKE symmetric fission, and the mechanisms of these three fissions should be very different. It is of great interest to elucidate how these differences occur. We have produced 
Fm in multinucleon-transfer reactions with a Es target and 
O projectiles, and produced Lr in the 
Cm(
N,4n) fusion-evaporation reaction. The reaction products were mass-separated with a gas-jet-coupled on-line isotope separator, and were delivered into a rotating wheel alpha- and fission-fragment detection system. By comparing the mass and TKE distributions deduced from the present experimental data, we will discuss the differences in fission mechanism among Fm, Fm, and Lr.
Es targetAsai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.
no journal, ,
Spontaneous fissions of neutron-rich heavy actinide isotopes Fm, Fm, and Lr have been measured at the JAEA Tandem accelerator facility. Fm and Fm were produced in a multinucleon transfer reaction with an O beam and an extremely rare Es target with a half-life of 276 days. Reaction products were mass-separated with an on-line isotope separator (ISOL). A transition between the typical asymmetric mass distribution and a very sharp symmetric one was clearly observed between Fm and Fm, while the spontaneous fission of Lr was found to exhibit mixture of three different fission modes.
Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi*; Tomitsuka, Tomohiro*; Chiera, N. M.*; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro*; Nishio, Katsuhisa; et al.
no journal, ,
We have studied spontaneous fission of neutron-rich Fm and Lr isotopes. The neutron-rich Fm isotopes were produced with the Es target and the O beam delivered by the JAEA tandem accelerator. The neutron-rich Lr isotope were produced with the Cm target and the N beam. Reaction products were mass-separated with an on-line isotope separator (ISOL), which enabled us to obtain non-contaminated samples and to measure fission fragments precisely. From the deduced fission-fragment mass and total kinetic energy distributions, we have obtained a new insight into the competition between the symmetric and asymmetric fission which is characteristic in this neutron-rich region.
Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi
no journal, ,
Asai, Masato
no journal, ,
Fission-fragment mass distributions and total kinetic energy (TKE) distributions for the spontaneous fission of Fm, Fm, Md, and Lr have been measured precisely. These nuclei were produced in the multinucleon transfer reactions with the O beam and the Es target, and in the fusion-evaporation reaction of Cm(N,4n)Lr at the JAEA tandem accelerator facility. The reaction products were mass-separated with the on-line isotope separator (ISOL), and the kinetic energies of spontaneous-fission fragments were measured with 4 pairs of Si semiconductor detectors. The results revealed that the three types of fission, the high-TKE and low-TKE symmetric fissions and asymmetric fission, compete or coexist in this neutron-rich Fm region.
MdAsai, Masato; Ishibashi, Yuichi*; Tsukada, Kazuaki; Sato, Tetsuya; Aoki, Ryota*; Ito, Yuta; Uchibaba, Yuta*; Orlandi, R.; Gong, G.-M.*; Suzaki, Fumi; et al.
no journal, ,
Measurement of mass and total kinetic energy (TKE) distribution for the spontaneous fission (SF) of Md has been performed to clarify the fission mechanism in the neutron-rich fermium region. Md nuclei were produced with the Es target and O beam, and mass-separated with an on-line isotope separator (ISOL). We discuss the mechanism of fission observed in the SF of Md on the basis of the observed mass-TKE distribution.
Asai, Masato
no journal, ,
Symmetric fission properties of neutron-rich transfermium nuclei have been studied through the measurements of spontaneous fission fragments of Fm, Md, and Lr. These nuclei were produced in the multinucleon transfer reactions with the O beam and the Es target, and in the fusion-evaporation reaction of Cm(N,4n)Lr at the JAEA tandem accelerator facility. The reaction products were mass-separated with the on-line isotope separator (ISOL), and the kinetic energies of spontaneous-fission fragments were measured with 4 pairs of Si semiconductor detectors. The deduced fission-fragment mass distributions and total kinetic energy distributions have revealed the detailed properties of symmetric fissions in this neutron-rich Fm and transfermium nuclei.
